American soldier on armored vehicle in Iraq
American soldier on armored vehicle in IraqReuters

An American soldier, a British soldier and one US contractor were killed on Wednesday in a rocket attack on an Iraqi military base hosting foreign troops, a US official told AFP.

Hours later, air strikes believed to have been carried out by the US-led coalition targeted Iran-aligned Iraqi fighters in neighboring Syria.

On Wednesday evening, a volley of rockets hit the Taji air base north of Baghdad, which hosts troops from the US-led coalition helping local forces battle jihadists.

A coalition official first told AFP the force had sustained "several" injuries on Wednesday ranging from "light to critical," but a US military official later confirmed three deaths.

The Iraqi military said the rockets were fired from the back of a truck, but it did not comment on any casualties.

There was no initial comment from Washington or London on those killed, nor was there an immediate claim of responsibility.

Washington has blamed Iran-backed factions from Iraq's Hashed al-Shaabi military network, which is incorporated into the Iraqi state, for similar violence in the recent past.

Within hours of Wednesday's attack, three warplanes likely belonging to the US-led coalition bombed Hashed factions stationed on the Syrian side of the border with Iraq, said the Britain-based Syrian Observatory for Human Rights.

"Ten explosions shook the area near Albukamal," said Observatory head Rami Abdel Rahman, citing a Syrian border town with a heavy Hashed presence.

Reports said that at lest 18 members of the pro-Iranian militia were killed in the US retaliatory air strike.

Hardline Hashed factions have fought alongside Syrian government forces for several years and have been targeted by both coalition and Israeli air strikes in Syria.

Wednesday's attack on the Taji air base was the 22nd on US installations in Iraq, including the American embassy, since late October.

Tensions have increased in the area since a rocket attack killed a US contractor working at a base in northern Iraq in late December.

Several days later, US F-15 fighter jets bombed five bases used by Kata'ib Hezbollah, a pro-Iranian Shiite group which straddles the boundary between Syria and Iraq, and is allied with the Lebanese terrorist group Hezbollah.

The tensions then continued when a US drone strike outside the Baghdad airport on January 3 killed the head of the Quds Force of the Iranian Revolutionary Guard, Qassem Soleimani, and the Hashed's deputy chief Abu Mahdi al-Muhandis.

Iran then retaliated by launching a volley of ballistic missiles at the western Iraqi base of Ain Al-Asad. While no US personnel were killed in that attack, at least 109 soldiers suffered from brain trauma.